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I am looking for any recommendations or suggestion for Ground Planes for two different grounds

I am designing a battery powered device with two voltage sources, 1 coming from the AC wall and other from a Li-ion battery when there is not energy available from the AC wall.

in the PCB design state I am facing a concern about the ground planes because it is very important for the design (reduce heat, impedance control, EMI) so I added a gas gauge to monitoring my battery state, but it requires a Rsense from the battery to my load. my question is now I have "two" different Ground separates for a miliOhm resistor, on stage for my DC-DC input converter and the other for the Battery to the load. is it right? how can I can handle the ground planes if one is "isolate" for a mOhm resistor.

should I keep my two different ground loops as small as possible?

Details: input 9V Load 5v/5A battery 3.7v (high current 15A max)

I added my Block diagram for the designenter image description here

any recommendation for monitoring the current in a different way? or any battery charger IC with gas gauge feature? Thanks

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You have to put the Rsense into the minus lead of the battery. I.e. It will see both charging and discharging current. And this will do nicely away with the split ground. Alternatively you can use a gas gauge with high side current sensing.

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  • \$\begingroup\$ I would like use a gas gauge with high side current sensing, but the only I could find are connected to minus. any suggestion for IC, digikey or mouser does not filter using this criteria. I would prefer this to keep a single power ground and not split in two different grounds to have a solid ground plane \$\endgroup\$ – Ale Sep 20 '17 at 21:12
  • \$\begingroup\$ I would have to search myself, so no suggestions from me. But as I wrote, you don't need to split ground if you put the resistor at the right place. \$\endgroup\$ – Attila Kinali Sep 20 '17 at 21:17

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